The present invention relates to a polymer-reinforced paper.
The reinforcement of paper by polymer impregnation is a long-established practice. The polymer employed typically is a synthetic material, and the paper can consist solely of cellulosic fibers or of a mixture of cellulosic and noncellulosic fibers. Polymer reinforcement is employed to improve one or more of such properties as dimensional stability, resistance to chemical and environmental degradation, resistance to tearing, embossability, resiliency, conformability, moisture and vapor transmission, and abrasion resistance, among others.
In general, the property or properties which are desired to be improved through the use of a polymer-reinforced paper depend on the application. For example, the resistance of a paper to tearing, e.g., the cross-direction tear as defined hereinafter, is particularly important when the paper is to be used as a base for making papers and tapes, abrasive papers for machine sanding, and flexible, tear-resistant marking labels, by way of illustration only.
Moreover, a property, such as resistance to tearing can be important for a given product under only certain conditions of use. By way of illustration, the cross-direction tear of a creped masking tape typically is directly proportional to the moisture content of the paper. When the tape is used under conditions of high relative humidity, the tape retains or absorbs moisture and the cross-direction tear usually is more than adequate. Under conditions of low relative humidity, however, such as those encountered during the high temperature curing of painted surfaces, the moisture content of the tape is reduced, with a concomitant reduction in cross-direction tear. When the tape is removed from a surface, slivering, or diagonal tearing of the tape, often occurs.
The use of polyhydric alcohols, including polyethylene glycols, is known in the papermaking art. For example, such materials have been applied locally to the cut edges of pulp sheet in order to reduce the formation of defibered knots. Such materials also have been incorporated in pulp sheets to impart improved dimensional and heat stability, softness and flexibility, wet tensile and wet tear strengths, and dimensional control at high humidities. They have been used to stabilize an absorbent batt of non-delignified fibers.
Such materials also have been used in methods of producing fluffed pulp and redispersible microfibrillated cellulose, to reduce the amount or carbon monoxide produced upon the burning of a cigarette paper, and in the preparation of a nonionic emulsifier useful as a sizing agent for paper.